A strict control of nitrate concentration in hydroponics during long-term experiments requires real-time analyses that cannot be performed manually. Adamowicz et al.describe a novel automatic set-up that measures and regulates nitrate concentration, pH and solution volume, allowing the calculation of nitrate uptake rates. The system is shown to be reliable at high temporal resolution (minutes to hours) and over long-term experiments (up to 1 year), and provides a method to regulate up to seven N treatments by adjusting the daily uptake of test plants relative to controls.